Circuit interrupter



Aug. 27, 1946. 1.. R. LUDWIG ET AL C IRCUIT INTERRUPTER Filed Nov. 11,1942 v INVENTORS L eon A. Ludwl 'g, Mnfhrap M. lead: & BenjamMRBa/rrATTOR zamamz- Patented Aug. 27, 1946 CIRCUIT IN TERRUPTER Leon R. Ludwigand Winthrop M. Leeds, Wilkinsburg, and Benjamin P. Baker, Turtle Creek,Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh,Pa., a corporation of Pennsylvania Application November 11, 1942, SerialNo. 465,244

2 Claims. (Cl. 200-150) This invention relates to and, moreparticularly, to are extinguishing structures therefor. Certain featuresof the invention are described and claimed in applicants divisionalapplication, filed December" 22, 1945, Serial No. 636,940, entitled,Circuit interrupters, and assigned to the assignee of the instantapplication.

Other features are described and broadly claimed in a divisional case,filed December 22, 1945, Serial No. 636,941, entitled Circuitinterrupters, and assigned to the assignee of the instant application.

More specifically our invention relates to a novel structure foreffecting the very rapid extinction of electric arcs drawn in circuitinterrupters. It is particularly applicable to the interruption of highvoltage arcs, such as those drawn in a 287 kv. circuit, and will effecttheir interruption in less than one cycle. Our invention is, however,not limited in its application only to high voltage circuits. It is alsoapplicable on low voltage circuits, but merely for purposes ofillustration it is described in the specification in a preferredembodiment as used on a high voltage circuit.

Extensive experimental investigation has clearly demonstrated that arapid lowering of the dielectric strength of an arc extinguishing fluid,such as oil, occurs after it impinges upon the arc stream. It istherefore desirable to eliminate such contaminated fluid as quickly aspossible, and to subject the arc stream to the action of fresh fluid ofhigh dielectric strength. It is one of the objects of our invention toprovide an arc extinguishing structure which makes full use of thisfact.

Another object of our invention is to provide improved piston meansassociated with the moving contact structure to effect the rapidextinction of low current arcs.

Another object is to provide an improved arc extinguishing structurewhich directs a plurality of radially inwardly flowing streams of fluidagainst the are, changes the direction of flow to one which islongitudinal of the arc, and then provides a plurality of radiallyoutflowing discharge streams which are substantially perpendicular tothe arc.

Another object is to provide an improved arc extinguishing structurewhich will produce both a pressure-generating arc and an interruptingarc, the pressure-generating are causing a plurality of inwardly flowingstreams to converge on the interrupting arc. Preferably the directioncircuit interrupters,

2 of flow of the inwardly flowing streams is changed to a directionwhich is longitudinal of the arc, anda plurality of venting passages areprovided for the rapid venting of contaminated fluid.

Another object is to provide an improved structure of the type describedin the immediately preceding paragraph in which piston means aredisposed between the two arcs to prevent contaminated fluid from thepressure-generating are coming in contact with the interrupting arc.

Another object is to provide an improved circuit interrupter whereinfluid adjacent to a pressure-generating arc is forced under pressuretoward the interrupting arc and to dispose piston means between the twoarcs, which piston means can be by-passed near the end of its travel.

Further objects and advantages will readily become apparent upon areading of the following description taken in conjunction with thedrawing, in which:

Fig. 1 is a side elevational view in cross section of a circuitinterrupter embodying our invention;

Fig. 2 is a side elevational view in cross section taken on the lineIIII of Fig. 1; and

Fig. 3 is a sectional view taken on the line III-III of Fig. 1.

Referring to the drawing and in particular to Fig. l, the referencenumeral I designates generally an arc extinguishing unit suspended fromone line terminal of the circuit interrupter in a suitable tank, notshown, and submerged in a suitable arc extinguishing fluid, such as oil.A conducting bridging bar I49 serves to connect electrically the arcextinguishing unit I with an identical unit, not shown, in a manner wellknown in the art.

We have found it desirable to rapidly vent ionized products ofdecomposition resulting from an arc extinguishing fluid impinging uponthe arc stream. After an arc extinguishing fluid strikes the arc stream,performing its de-ionizing function by turbulently breaking up andcooling the ionized arc path, contamination of the fluid decreases itsusefulness for further extinguishing and. insulating purposes. We have,therefore, found it desirable to subject the arc stream to a pluralityof radially infiowing streams of arc extinguishing fluid at a number ofpoints along the length of the arc stream rather than to use a singlestream to de-ionize a considerable length of arc. At a number ofintermediate points along the arc stream, we provide a plurality ofvents to allow the contaminated fluid to be rapidly vented radiallyoutward from the arc space.

Preferably the inflowing fluid which strikes the arc stream shouldstrike the arc radially thereof from at least opposite sides to maintainthe arc stream in a central position away from adjacently disposedinsulating surfaces. If an arc contacts an insulating surface it tendsnot only to burn away the insulating surface but also to leave carbonthereon which has conducting properties. In the construction of ourinvention we preferably maintain the are away from -adjacently disposedinsulating walls by subjecting at least opposite sides of the arc streamto a radially inward flow of fluid.

In this embodiment of our invention, a plurality of insulating platesare pressed togther to form an insulating arcing structure havingentrance and vent passages more fully described hereinafter, Tie rods 62hold the insulating plate rigidly in position. A resiliently mountedrelatively stationary contact I42 is provided which cooperates with anintermediate contact member I43 to draw a pressure generating arc I44,as more clearly shown in Fig. 2. The intermediate contact I43 hassecured thereto at its lower end a metallic spider member I45 whichserves as a lower seat for a battery of compression springs I46.Cooperating with the intermediate contact I43 to draw an interruptingarc I48 (see Fig. 2) is a lower movable contact I41. A conductingbridging member I49 operates the lower movable contact I41. Suitableoperating mechanism, not shown, actuates the conducting bridging memberI49. A flexible conductor I56 electrically connects the stationarycontact I42 with a top metallic plate I51 which, in this instance, is anintegral portion of the contact foot I 52.

It will be apparent that in the closed-circuit position of theinterrupter shown in Fig. 1, the electrical circuit therethroughcomprises the contact foot I52, the top metallic plate II, flexibleconductor I50, relatively stationary contact I42, intermediate contactI43, lower movable contact I41 and conducting bridging member I49, fromwhence the circuit passes through another identical arc extinguishingunit, not shown, to the other terminal of the interrupter.

Rigidly secured by contact button I53 to the intermediate contact I43 isa metallic valve plate I54. A perforated metallic piston I55 has alimited permissible sliding movement with respect to'the intermediatecontact I43 as determined by the metallic valve plate I54 and integrallyformed shoulders I56 formed on the intermediate contact I43.

When the interrupter is in the closed-circuit position, as is shown inFig, 1, the battery of compression springs I46 is compressed, metallicpiston I55 rests upon the shoulder I56 and the valve I51 is opened. Whenit is desired to open the electrical circuit through the interrupter,suitable operating mechanism, not shown, moves the conducting bridgingbar I49 downward. The intermediate contact I43 being strongly biaseddownward by the compression springs I46 rapidly follows the initialdownward movement of the lower movable contact I41 to result in themetallic valve plate I54 closing the apertures in the perforated pistonI55, the piston I55 remaining practically stationary during this timebecause of the dashpot action. During the initial movement, theresiliently mounted stationary contact I42 follows the initial movementof the intermediate contact I43 until the shoulder I58 on the stationarycontact I42 strikes the insulating plate I59. Further downward movementof the lower movable contact I41 draws substantially simultaneously botha pressure-generating arc I44 and an interrupting arc I48, as moreclearly shown in Fig.2.

It would, of course, be possible to have the two arcs formedsequentially by raising the position of the insulating plate I59. Inthis event the pressure-generatingarc I44 would be formed first, and theresulting pressure would help to drive the piston I55 downward.

During the interruption of low currents, the pressure generated by thepressure-generating arc I44 will be relatively low and reliance for thefluid motion is placed on the compression springs I46. The downwardmovement of the piston I 55 causes oil to flow as indicated by thearrows I66 in Fig. 1. The fluid flows downwardly as caused by the pistonI55 through two kidneyshaped vertical flow passages generally designatedby the reference numerals 2 provided in the plurality of contiguouslydisposed insulating plates, as shown more clearly in Fig. 3. Afterpassing downwardly through the two vertically disposed fiow passages 2,the fluid passes radially inwardly toward the interrupting arc 148through a plurality, in this, instance four, inlet passages 3 providedby a pair of insulating inlet plates 4 having a configuration moreclearly shown in Fig. 3. The fluid after contacting the interrupting arcI48 passes upwardly and downwardly through adjacently disposed orificeplates 5 and out of the arc-extinguishing unit I through vent passagesI61 disposed substantially at right angles to the direction of the inletpassages 3. The vent passages I61 are formed by insulating vent plates1, which also provide an insulating orifice 8 of substantially the samediameter as the orifice provided by the insulating orifice plates 5.Thus, the orifices 8 provided by the insulating orifice plates 5 and theinsulating vent plates 1 cause the arc-extinguishing fiuid to flowlongitudinally of the interrupting arc I48 intimately contactingtherewith before this arc-extinguishing fluid is vented out of thearc-extinguishing unit I through the oppositely disposed ventingpassages I61 as provided by the vent plates 1.

Certain features of the flow passage arrangement are described andbroadly claimed in U. S. patent application, Serial No. 574,856, filedJanuary 27, 1945, by Winthrop M. Leeds and Benjamin P. Baker, andassigned to the assignee of the instant invention.

During the interruption of high short-circuit currents, the pressuregenerated by the pressure-.

generating arc I44 will assist the compression springs I46 in moving thepiston I55 downwardly to cause an increased fluid flow toward theinterrupting arc I48.

It will be observed that when the perforated metallic piston I55 strikesthe insulating plate I6 I, as shown by the dotted lines in Fig. 1, fluidfrom the pressure-generating arc I44 may continue to flow past theperforated plate I55 in the annular space indicated by the referencenumeral I62. On the interruption of high currents, this bypassing actionis of advantage for arc interruption which possibly may not haveoccurred by the time the perforated plate I55 has come to rest, andfurther fluid motion caused by the pressure generating arc I44 istherefore desirable.

It will be observed that in this embodiment of our invention, we haveprovided annular pockets I65 disposed between the inlet passages and thevent passages. The annular pockets 55 provide a readily availablequantity of oil adjacent the arc path, and also the annular pockets I65break up the insulaitng surfaces adjacent to the are I 43 to minimizethe possibility of carbonization of these insulatin surfaces.

We have provided a plurality, in this instance two, additional annularoil-retaining pockets I65 at the lower end of the structure between thelower venting passages IE1 and the bottom insulating plate I58. It isdesirable to maintain an increased pressure within the arcing region,for the dielectric strength of an arc extinguishing fluid depends notonly on the degree of ionization therein but also on the pressure,increased pressure causing increased dielectric strength. We have foundthat the provision of the oil-retaining pockets IE6 reduces the gas andfluid leakage by making the how more turbulent as the lower movablecontact MT is Withdrawn out of the are extinguishing structure.

The concept of securing a piston to an intermediate contact disposed inan arc extinguishing unit of the type which produces both apressuregenerating arc and an interrupting arc is described and broadlyclaimed in an application filed September 18, 1942, Serial No. 458,778,by Winthrop M. Leeds and Benjamin P. Baker, now U. S. Patent 2,372,589,issued March 27, 1945, and assigned to the assignee of the instantapplication. Also an application filed December 26, 1942, Serial No.470,161, by John B. MacNeill and assigned to the assignee of the presentapplication describes certain improvements in the concept of operativelyconnecting a piston to an intermediate contact in an arc extinguishingstructure of the type producing both a pressure generating are and aninterrupting arc.

Although We have illustrated a specific embodiment, it will be clearlyunderstood that the same was merely for purpose of illustration and thatchanges and modifications may be made therein by those skilled in theart without departing from the spirit and scope of the appended claims.

We claim as our invention:

1. In a circuit interrupter, a relatively stationary contact, anintermediate contact, a moving contact, the intermediate contact beingcooperable with the stationary contact to produce a pressure-generatingarc, the intermediate contact being cooperable with the moving contactto draw an interrupting arc, passage means extending between thepressure generating arc and the interrupting arc, a piston operativelyconnected to the intermediate contact and movable therewith, the pistonmaking a comparatively tight fit With the walls of the passage meansduring the initial movement thereof, an enlarged portion in the passagemeans operative after the piston has neared the end of its travel topermit a by-passing of fluid past the piston, the fluid pressure createdby the pressure generating arc assisting in the extinguishment of theinterrupting arc.

2. In a circuit interrupter, a relatively stationary contact, anintermediate movable contact, a movable contact, the stationary contactand the intermediate contact cooperating to es- .tablish apressure-generating arc, the intermediate contact and the movablecontact being cooperable to establish an interrupting arc, a pressurechamber adjacent the pressure-generating arc, an interrupting passageadjacent the interrupting arc, passage means extending between thepressure chamber and the interrupting passage, piston means operativelyattached to and movable With the intermediate contact, valve means forthe piston means operative upon the initial movement of the intermediatecontact, the piston means extending across the passage means during theinitial movement thereof, an enlarged portion in the passage means, theenlarged portion being so disposed that during the end of the travel ofthe piston means a Icy-passing of fluid around the piston means ispermissible.

LEON R. LUDWIG. WINTHROP M. LEEDS. BENJAMIN P. BAKER.

